Heart failure (HF) is a debilitating, end-stage disease in which abnormal function of the heart leads to inadequate blood flow to fulfill the needs of the body's tissues. Typically, the heart loses propulsive power because the cardiac muscle loses capacity to stretch and contract. Often, the ventricles do not adequately fill with blood between heartbeats, and the valves regulating blood flow may develop leaks, allowing regurgitation or backflow of blood. The impairment of arterial circulation deprives vital organs of oxygen and nutrients. Fatigue, weakness, and inability to carry out daily tasks may result. Not all HF patients suffer debilitating symptoms immediately. Some may live actively for years. Yet, with few exceptions, the disease is relentlessly progressive. As HF progresses, it tends to become increasingly difficult to manage.
Using temporary induced dyssynchrony (TID) therapy to create regular, periodic asynchrony in HF patients without underlying dyssynchrony has been shown to facilitate improvement of the cardiac chamber function, cellular function, and cardiac reserve. Specifically, at least some known TID therapy, such as pacemaker-induced transient asynchrony (PITA) therapy that uses a pacemaker to induce asynchrony, involves using right ventricular (RV) pacing to induce forced ventricular asynchrony in a patient's heart at regular intervals (e.g., for a period of six hours every night for six weeks). One concept behind TID therapy is that the heart may benefit from “exercise” (i.e., forcing the heart into ventricular asynchrony), similar to other muscles in the body.
For HF patients that do have existing dyssynchrony, cardiac resynchronization therapy (CRT) pacing is an established treatment. Specifically, CRT pacing includes the delivery of multiple ventricular pacing pulses to improve cardiac function by increasing the synchrony of the ventricle. Traditionally, CRT has included biventricular (BiV) pacing in which one pacing pulse is delivered to the left ventricle and one pacing pulse is delivered to the right ventricle. Recently, multi-point pacing (MPP) has been implemented as an option that may provide increased clinical benefits compared to BiV pacing. MPP includes delivering two pacing pulses to the left ventricle and one pacing pulse to the right ventricle. The delivery of the extra left ventricular (LV) pacing pulse in MPP may further increase synchrony and thus further improve clinical response.
Both TID therapy and CRT are beneficial due to the cellular response associated with a transition from asynchrony to synchrony. Patients receiving CRT generally already have natural dyssynchrony, and CRT induces synchrony. In contrast, TID therapy, specifically PITA therapy, induces periodic asynchrony via pacing and a transition to synchrony when the pacing stops. However, TID therapy may provide benefits to CRT patients, but the delivery of the TID therapy may need to be altered to achieve those benefits.